Add mix testing to nearest_neighbor
Add mix testing to nearest_neighbor

kumagi/jubatus_core,gintenlabo/jubatus_core,gintenlabo/jubatus_core,kumagi/jubatus_core,kumagi/jubatus_core,rimms/jubatus_core,kumagi/jubatus_core,gintenlabo/jubatus_core,gintenlabo/jubatus_core,rimms/jubatus_core,rimms/jubatus_core,rimms/jubatus_core